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Fencer Vulns
critical 9.8

CVE-2018-20721 json

URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6…

published 2019-01-16 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-13266

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.1%
EPSS 2.1% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

URI_FUNC() in UriParse.c in uriparser before 0.9.1 has an out-of-bounds read (in uriParse*Ex* functions) for an incomplete URI with an IPv6 address containing an embedded IPv4 address, such as a "//[::44.1" address.

Patch / fix

  • uriparser_project uriparser 0.9.1
  • uriparser Debian 14, Debian 13, Debian 12 0.9.1-1

debian advisories DEBIAN-CVE-2018-20721

  • uriparser Ubuntu 18.04 LTS 0.8.4-1+deb9u2build0.18.04.1
  • uriparser Ubuntu Pro 14.04 LTS 0.7.5-1ubuntu2+esm2
  • uriparser Ubuntu Pro 16.04 LTS 0.8.4-1ubuntu0.16.04.1~esm2

ubuntu advisories UBUNTU-CVE-2018-20721

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • uriparser openSUSE Tumbleweed 0.9.5-1.2
  • uriparser openSUSE Leap 15.0 0.8.5-lp150.2.3.1
  • uriparser Package Hub 15 0.8.5-bp150.2.3.1

opensuse advisories openSUSE-SU-2024:11488-1openSUSE-SU-2019:0165-1openSUSE-SU-2019:0171-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-20721 updated cvss 5.3

uriparser: Out-of-bounds read in uriParse*Ex*

  • Red Hat Enterprise Linux 7 uriparser
    affected: no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.05% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.